The present invention relates generally to systems for controlling engine and/or vehicle operation, and more specifically to such systems operable to control engine and/or vehicle operation while descending negative grades.
Many modern heavy duty tractor trucks include engine compression brakes operable to apply retarding torque to internal combustion engines carried by the trucks during prescribed operating conditions. Such engine compression brakes are typically used to assist in decreasing engine and/or vehicle speed in addition, or alternatively, to the vehicle service brakes. Engine compression brake technology has been well received and is widely used, particularly in the heavy duty diesel engine industry, and operational details thereof are well known.
When a tractor truck operator encounters a steep downhill or negative grade, known technology typically requires the operator to carefully exercise control over the engine compression brakes, service brakes and downshifting of the vehicle transmission to thereby maintain a controlled descent down the hill. As this term is used herein, xe2x80x9ccontrolled descentxe2x80x9d is understood to define a downhill vehicle operating condition wherein engine or vehicle speed is maintained substantially at a target engine or vehicle speed. Such descents, however, are largely a function of the vehicle operator""s experience, and a runaway vehicle condition may result when an operator loses control over engine/vehicle speed while descending the grade. Most steep negative grades accordingly include run-off areas that provide a steep uphill vehicle path or other means for maneuvering the vehicle out of harm""s way while also providing for increasing engine/vehicle retarding force due to the steep positive incline or other vehicle slowing/stopping means. Concern over runaway vehicle conditions may be heightened as transmissions in heavy duty tractor trucks become more automated since vehicle operators may become increasingly reliant on automated shifts, and hence the capability of manually downshifting to a numerically lower gear may become increasingly overlooked. Currently, no systems are known for automatically controlling engine/vehicle speed to thereby provide for a controlled descent under potential runaway vehicle conditions.
There also exist other conditions where it would be desirable to provide for a controlled descent down a negative grade at an engine/vehicle speed that is different from current engine/vehicle speed conditions. As a specific example, a vehicle operator may crest a steep downhill grade at a first vehicle speed (e.g. 55 mph), and desire to descend the grade at a lesser second vehicle speed (e.g. 40 mph) due to current weather conditions, changing speed limit restrictions or the like. While the vehicle operator may have no trouble in achieving the lesser second vehicle speed via proper control over engine compression brakes, service brakes and/or transmission gear shifting, no systems are currently known for automatically providing for a controlled descent down a negative grade at a selected engine/vehicle speed.
What is therefore needed is a system for automatically controlling engine/vehicle speed to thereby provide for a controlled descent down a negative grade. Such a system should ideally provide for a controlled descent under potential runaway vehicle conditions and further under conditions specified by the vehicle operator to thereby provide for a controlled descent at a desired engine/vehicle speed.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a system for controlling downhill vehicle operation, comprises means for determining a potential runaway vehicle condition, an engine compression brake associated with an internal combustion engine for retarding engine operation, a service brake associated with a vehicle carrying the engine, a transmission coupled to the engine and having a number of automatically selectable gear ratios, and a control computer responsive to detection of the potential runaway vehicle condition to control the engine compression brake, the service brake and selection of the number of automatically selectable gear ratios of the transmission to thereby control one of engine and vehicle speed to prevent a runaway vehicle condition.
In accordance with another aspect of the present invention, a method of controlling downhill operation of a vehicle carrying an internal combustion engine having an engine brake and coupled to a transmission having a number of automatically selectable gear ratios, comprises the steps of determining whether a potential runaway condition exists for a vehicle carrying an internal combustion engine coupled to a transmission having a number of automatically selectable gear ratios, and performing the following steps if the potential runaway condition exists; determining one of a current engine and vehicle speed, and controlling any of an engine brake associated with the engine, a service brake associated with the vehicle and selection of the number of automatically selectable gear ratios of the transmission to thereby maintain one of a current engine and vehicle speed at a substantially constant speed value for a duration of the potential runaway condition.
In accordance with yet another aspect of the present invention a system for controlling downhill vehicle operation comprises an engine compression brake associated with an internal combustion engine for retarding engine operation, a service brake associated with a vehicle carrying the engine, a transmission coupled to the engine and having a number of automatically selectable gear ratios, means for determining one of a target engine and vehicle speed, means for determining whether the vehicle is traversing a negative grade, and a control computer responsive to detection of the vehicle traversing a negative grade to control any of the engine compression brake, the service brake and selection of the number of automatically selectable gear ratios of the transmission to thereby control one of engine and vehicle speed to a corresponding one of the target engine speed and the target vehicle speed.
In accordance with a further aspect of the present invention, a method of controlling downhill operation of a vehicle carrying an internal combustion engine having an engine brake and coupled to a transmission having a number of automatically selectable gear ratios, comprises the steps of determining whether the vehicle is traversing a negative grade, determining one of a target engine speed and a target vehicle speed, performing the following steps if the vehicle is traversing a negative grade, determining one of a current engine and vehicle speed, and controlling any of an engine brake associated with the engine, a service brake associated with the vehicle and selection of the number of automatically selectable gear ratios of the transmission to thereby control one of current engine and vehicle speed to a corresponding one of the target engine speed and the target vehicle speed.
In accordance with still another aspect of the present invention, a system for controlling downhill vehicle operation, comprises means for determining a potential runaway vehicle condition, a service brake associated with a vehicle carrying the engine, a transmission coupled to the engine and having a number of automatically selectable gear ratios, and a control computer responsive to detection of the potential runaway vehicle condition to control the service brake and selection of the number of automatically selectable gear ratios of the transmission to thereby control one of engine and vehicle speed to prevent a runaway vehicle condition.
In accordance with still a further aspect of the present invention, a system for controlling downhill vehicle operation, comprises an engine compression brake associated with an internal combustion engine for retarding engine operation, means for determining one of a target engine and vehicle speed, a service brake associated with a vehicle carrying the engine, a transmission coupled to the engine and having a number of automatically selectable gear ratios, and a control computer responsive to determination of the target engine or vehicle speed and to activation of the engine compression brake to control the service brake and selection of the number of automatically selectable gear ratios of the transmission to thereby control one of engine and vehicle speed to the target engine or vehicle speed.
In accordance with yet a further aspect of the present invention, a system for controlling downhill vehicle operation, comprises an engine compression brake associated with an internal combustion engine carried by a vehicle, means for determining a potential runaway vehicle condition, and a control computer responsive to detection of the potential runaway vehicle condition to control the engine compression brake to thereby control one of engine and vehicle speed to prevent a runaway vehicle condition.
In accordance with yet another aspect of the present invention, a system for controlling downhill vehicle operation, comprises an engine compression brake associated with an internal combustion engine for retarding engine operation, means for determining one of a target engine and vehicle speed, and a control computer responsive to determination of the target engine or vehicle speed and to activation of the engine compression brake to control the engine compression brake to thereby control one of engine and vehicle speed to the target engine or vehicle speed.
One object of the present invention is to provide a system and method for controlling downhill vehicle operation by controlling an engine compression brake, vehicle service brakes and/or selection of a number of automatically selectable gear ratios of a transmission coupled to the vehicle engine, to thereby achieve a target engine or vehicle speed and provide for a controlled descent down the hill.
Another object of the present invention is to provide such a system operable to control downhill vehicle operation by further controlling turbocharger boost pressure to thereby achieve the target engine or vehicle speed.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.